Invited Presentations Invited Abstracts

TC07.02 - MRI Predictors of Cognitive Impairment (ID 608)

Speakers
  • B. Brochet
Authors
  • B. Brochet
Presentation Number
TC07.02
Presentation Topic
Invited Presentations

Abstract

Abstract

Several magnetic resonance imaging (MRI) studies have been performed to characterize the pathological abnormalities associated with cognitive impairment (CI), using both morphological and functional analyses.

For a better understanding of the role of the different mechanisms involved in CI, it could be worth to study specific cognitive domains separately and to focus on early stages when all mechanisms could be more easily disentangled. Indeed, when considering the two more frequent cognitive processes impaired at the early stage of the disease, Information processing speed (IPS) and memory, different mechanisms could be discussed. At this early stage of the disease, the role of focal lesions, network disruption or gray matter (GM) vulnerability has been suggested. IPS depend on the integrity of large-scale cortical integrative processes, which involve long-distance white matter projections which can be impaired due to diffuse demyelinating injury in patients (focal lesions) and the axonal pathology related to these lesions. In early RRMS the correlation of CI with lesion load is no longer significant when diffuse white matter pathology (normal appearing white matter magnetization transfer ratio or DTI metrics) are taken into account suggesting that disconnection play an important role in CI, mainly in IPS deficits. The involvement of several key brain regions has been shown, contributing to these deficits, such as the thalamus, the cerebellum and default mode network. Episodic memory impairment is associated with deep GM injury in the limbic system, in particular the hippocampi and the basal ganglia. The growing role, along the disease course, of GM pathology spreading initially in regions with more vulnerability in deep GM and the cortex and leading to progressive brain atrophy could explain the deterioration of memory or other domains like executive functions.

Functional MRI studies gave evidence of brain reorganization at these early stages suggesting the presence of compensatory mechanisms. The evolution of structure-function relationships during the early stages of MS and their role in cognitive performance have been studied recently. Alteration of structural-functional coupling could contribute to network collapse associated with a decline in cognitive status.
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